r.external.out - GRASS GIS manual

NAME

r.external.out - Redirects raster output to file utilizing GDAL library rather than storing in GRASS raster format.

KEYWORDS

SYNOPSIS

r.external.out

r.external.out --help

r.external.out [-frp] directory=path [extension=string] format=string [options=string[,string,...]] [--help] [--verbose] [--quiet] [--ui]

Flags:

-f: List supported formats and exit
-r: Cease using GDAL and revert to native output
-p: Print current status
--help: Print usage summary
--verbose: Verbose module output
--quiet: Quiet module output
--ui: Force launching GUI dialog

Parameters:

directory=path [required]: Name of output directory
extension=string: Extension for output files
format=string [required]: Format of output files; Options: VRT, GTiff, COG, NITF, HFA, ELAS, AAIGrid, DTED, PNG, JPEG, MEM, GIF, FITS, XPM, BMP, PCIDSK, PCRaster, ILWIS, SGI, SRTMHGT, Leveller, Terragen, GMT, netCDF, HDF4Image, ISIS3, ISIS2, PDS4, VICAR, ERS, JP2OpenJPEG, FIT, GRIB, RMF, WMS, RST, INGR, GSAG, GSBG, GS7BG, R, KMLSUPEROVERLAY, WEBP, PDF, Rasterlite, MBTiles, CALS, WMTS, MRF, PNM, PAux, MFF, MFF2, BT, LAN, IDA, LCP, GTX, NTv2, CTable2, KRO, ROI_PAC, RRASTER, BYN, ARG, USGSDEM, BAG, NWT_GRD, ADRG, BLX, EPSILON, PostGISRaster, SAGA, XYZ, HF2, JPEGLS, ZMap, SIGDEM, GPKG, NGW, ENVI, EHdr, ISCE
options=string[,string,...]: Creation options

DESCRIPTION
NOTES
EXAMPLES
- Storing results from raster data analysis directly as GeoTIFF
- Complete workflow using only external geodata while processing in GRASS GIS
REFERENCES
SEE ALSO
AUTHOR

DESCRIPTION

r.external.out instructs GRASS GIS to write subsequently generated raster maps as data files (e.g. GeoTIFF) using GDAL instead of storing them in GRASS raster format in the current mapset.

Any new raster map is immediately written out through GDAL as a file.

A relative directory path (parameter directory) is interpreted relative to the current mapset directory, not the current directory where the command was launched. An unspecified or empty directory (which will occur if the user passes a simple filename for output) results in the output file being placed in the "gdal/" subdirectory of the current mapset directory.

EXAMPLES

Storing results from raster data analysis directly as GeoTIFF

The module r.external.out is used to write out processing results directly in GeoTIFF format (any GDAL supported format can be used here):

# define output directory for files resulting from GRASS calculation(s)
# and target format:
mkdir $HOME/gisoutput/
# hint: the create options are not mandatory
r.external.out directory=$HOME/gisoutput/ format="GTiff" option="BIGTIFF=YES,COMPRESS=DEFLATE"
# prepare sample analysis
g.region raster=elevation -p

# perform GRASS calculation (here: filter by height, write > 120m, NULL otherwise)
# this will store the output map directly as GeoTIFF, so we use .tif extension:
r.mapcalc "elev_filt.tif = if(elevation > 120.0, elevation, null() )"

# ...the "elev_filt.tif" is immediately written.

# cease GDAL output connection and turn back to write out GRASS raster files:
r.external.out -r

# verify resulting file
gdalinfo $HOME/gisoutput/elev_filt.tif

Complete workflow using only external geodata while processing in GRASS GIS

The module r.external.out can be used along with r.external to process external geodata in GRASS while writing out the results directly in GeoTIFF:

# register GeoTIFF file to be used in current mapset:
r.external input=terra_lst1km20030314.LST_Day.tif output=modis_celsius

# define output directory for files resulting from GRASS calculation:
r.external.out directory=$HOME/gisoutput/ format="GTiff"

# perform GRASS calculation (here: extract pixels > 20 deg C)
# this stores the output map directly as GeoTIFF:
r.mapcalc "warm.tif = if(modis_celsius > 20.0, modis_celsius, null() )"

# cease GDAL output connection and turn back to write GRASS raster files:
r.external.out -r

# now use the resulting file elsewhere
gdalinfo $HOME/gisoutput/warm.tif

REFERENCES

GDAL Pages: https://gdal.org/

AUTHOR

Glynn Clements

SOURCE CODE

Available at: r.external.out source code (history)

Latest change: Wednesday Nov 27 22:53:26 2024 in commit: 3b5486c0463a7103ab2109e28bf860fe34539868